1. Field of Invention
The present invention relates to a wireless communication device. More particularly, the present invention relates to a wireless communication device which only needs a single antenna and a plurality of switches to realize multi-band operation.
2. Description of Related Art
With rapid development in WLAN, multimode operations or multi-band operations have gradually become more mature. Currently, common WLAN standards include 802.11a, 802.11b and 802.11g. The 802.11a WLAN standard operates at 5.2 GHz, while the 802.11b and 802.11g WLAN standards operate at 2.4 GHz.
These WLAN standards have their own advantages, operational features and cost features, and certainly disadvantages. The multimode operation can integrate the advantages of these standards, and make up for the disadvantages.
For example, the multimode operation at least has the following advantages. Firstly, the multimode operation may be advantageous in terms of the cost. Secondly, the multimode operation supports various transmission speeds, which best satisfies future market demands. Thirdly, the multimode operation meets different power requirements at the same time. Fourthly, the multimode operation satisfies the requirements on the coverage scope and data transmission speed simultaneously.
To realize the multimode/multi-band operation, two sets of RF signal transceivers are adopted in a conventional WLAN card or WLAN router. Each set of RF signal transceiver has to be used together with a spiral inductor antenna. FIG. 1 is a schematic view of a dual-band WLAN card. The dual-band WLAN card can operate at 2.4 GHz and 5.2 GHz. When operating at 2.4 GHz, an RF transceiver 101 and a spiral inductor antenna 103 are used to receive and transmit 2.4 GHz RF signals. In another aspect, when operating at 5.2 GHz, an RF transceiver 102 and a spiral inductor antenna 104 are used to receive and transmit 5.2 GHz RF signals. It should be noted that the inductance values and Q values of the spiral inductor antennae 103, 104 are different.
Though the dual-band WLAN card is not difficult to design, the circuit area thereof cannot be easily reduced, as an inductor occupies a large area in the circuit layout, and the dual-band WLAN card needs two inductors of different inductance values and different Q values to realize the desired dual-band operation.
Therefore, it is preferred to develop a wireless communication device (such as a WLAN card or a WLAN router) operating at dual-band or even multi-band with a small circuit area.